1 answer

The issue transitioning happens after the pull request is merged. If the issue is missing the required field, you will still be able to merge the pull request, but the issue won't be transitioned into the resolved state (because JIRA won't do it).

If you want to prevent the pull request from being merged, you can build a plugin to block it by using a MergeRequestCheck. You can find documentation and examples on http://developer.atlassian.com: